Add additional post flag validation preventing targeting

app/logical/danbooru_math.rb

@@ -0,0 +1,11 @@
+class DanbooruMath
+  def self.ci_lower_bound(pos, n, confidence = 0.95)
+    if n == 0
+      return 0
+    end
+
+    z = Statistics2.pnormaldist(1-(1-confidence)/2)
+    phat = 1.0*pos/n
+    100 * (phat + z*z/(2*n) - z * Math.sqrt((phat*(1-phat)+z*z/(4*n))/n))/(1+z*z/n)
+  end
+end